控制水稻內外穎發育SLP 基因座之 高解析度遺傳定位與候選基因鑑定

Abstract

Stunted lemma/palea (slp) 為一由疊氮化鈉誘變所得之水稻突變品系，其外表型呈現矮株、內外穎退化與不稔。藉由SLP的選殖與功能分析將有助於探討禾本科植物內外穎的發育與起源。在本論文中，遺傳分析結果證實slp為單一基因控制的突變，此突變並多方面地影響了水稻株高、花穗發育、與其他的外表性狀。除株高外，slp等位基因座對於多數性狀皆呈現不完全顯性的遺傳。本論文以82個具多型性的SSR分子標誌，針對42株由slp突變系與台中在來一號雜交所獲得的F2族群，進行SLP的基因定位。此結果將SLP基因定位於水稻第八條染色體末端介於分子標誌RM23477與RM23652之間的區域。隨後以134株F2植株對此區間進行遺傳圖譜分析，將SLP基因的定位區間縮小至分子標誌RM447與D275之間。接著以982株F2植株進行高解析度的遺傳圖譜分析，將SLP基因定位於一段46.4 kb的染色體區間內。此區間經基因比對及註解後，發現有三個候選基因: OsSPL16、OsMADS45 (OsMADS7) 與 OsMADS37。針對此三個候選基因，進行SLP/SLP與slp/slp基因型個體之間的核酸序列比對以及基因表現量的比較。結果顯示影響slp突變外表型最可能的原因是OsSPL16 蛋白序列的第六個胺基酸產生錯義突變。

Stunted lemma/palea (slp) is a sodium azide-induced rice mutant displaying dwarf, shorten panicle length, seriously degenerated lemma/palea, and sterility. Cloning and characterization of the SLP locus may shed light on the molecular basis and evolutionary history of glume development in grass. Genetic analysis confirmed that slp phenotype was controlled by a single gene with pleiotropic effect on plant height and several traits related to inflorescence architecture. The slp mutant allele was incomplete dominant to the normal allele for most of affected traits but plant height. Genetic mapping based on the genotypes of 82 polymorphic SSR markers in 42 F2 plants which was derived from the cross between SLP/slp (Oryza sativa subsp. japonica) and Taichung native 1 (O. sativa subsp. indica), suggested that the SLP locus was mapped between markers RM23477 and RM23652 in the distal region of the long arm chromosome 8. Additional 134 F2 individuals were used to delimit the SLP locus in a smaller chromosomal region between marker RM447 and D275. A high-resolution genetic map surrounding the SLP locus was developed using 8 recombinant F2 individuals screened from 982 F2 plants. The SLP locus was eventually delimited in a 46.4 kb genomic region containing three putative genes, OsSPL16, OsMADS45 (also known as OsMADS7)and OsMADS37. Detection of single nucleotide polymorphism and comparisons of gene expression level between the SLP/SLP and slp/slp genotypes for three candidate genes suggested that a missense mutation at the sixth amino acid of the OsSPL16 protein was likely responsible for the slp mutant phenotypes.